The hardest hole for me is Oakmont #9, although I agree that the various other holes mentioned on this thread are all tough, however the OP's question was not 'toughest' but 'least favourite' hole.
So to directly answer the question I'd have to say #10 at CCC and #17 at Kia. Neither is especially tough, but if you are using Nike balls and the meter sticks, you say goodbye instantly to $1.50. Now THAT annoys me more than any bogie!